The invention concerns a fuel circuit with thermostat-controlled fuel preheating for preferably air-compressing injection-type internal combustion engines of the type having cooling water ducts extending in the engine cylinder head.
Fuel circuits with measures for heating the fuel are sufficiently known. European Patent Document No. EP 0 258 529 A2, for example, shows a heat exchanger and a switch-over valve which are combined into one structural unit and are inserted in an intermediate position in a cooling water conduit and a fuel conduit. In the heat exchanger with connections for the water inlet and water outlet, ducts for the cooling water and for the fuel controlled by the adjacent switch-over valve extend separately from one another.
The invention is based on the object of simplifying the thermostat-controlled fuel preheating of the generic type with simultaneous reduction of weight and space requirements.
This object is achieved, in accordance with the invention, by means of an arrangement comprising:
a supply conduit starting from a fuel tank and leading via a fuel filter to a fuel injection pump,
a heat exchanger,
a switch-over valve in the supply conduit with an expanding-material operating element for controlling the switch-over valve as a function of fuel temperature and guiding the fuel through the heat exchanger at low ambient temperatures, the heat exchanger and the switchover valve being combined into one structural unit,
wherein the switch-over valve and the heat exchanger through which only fuel is intended to flow, are fastened to the cylinder head in such a way that the heat exchanger protrudes into the cooling water flow of the cooling water duct extending in the cylinder head.
By means of the special arrangement of the structural unit consisting of the heat exchanger and the switch-over valve, i.e., immersing the heat exchanger protruding from the switch-over valve in the cooling water flow in the cylinder head, the external cooling water conduits become unnecessary. In addition, only the installation space for the switch-over valve with the fuel conduits protruding from the cylinder head into the engine compartment is required.
Other advantageous features of the invention are described in conjunction with the following description and claims.
By means of the special type of fastening according to preferred embodiments of the invention, it is possible to exchange the switch-over valve in a simple manner without removing the heat exchanger in the case of a defect in the thermostat. Cooling water cannot run out during the exchanger procedure.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.